Inventory Accuracy in Manufacturing: 6 Causes and Fixes

Quick answer: Inventory accuracy in manufacturing drops when transactions are recorded late, scrap goes unreported, or bills of materials (BOMs) don’t match how products are really built. The fix combines three habits: record transactions at the point they happen, count the most important items often through cycle counting, and find the root cause of every error instead of just correcting the number.

Your ERP system says there are 400 units on the shelf. The storekeeper finds 260. Production stops while purchasing expedites a rush order, and the planner adds a little extra safety stock next time, just in case.

This story plays out in factories across Malaysia and Singapore every week. Inaccurate inventory doesn’t just cause shortages. It leads to excess stock, emergency freight, missed delivery dates, and a planning system that nobody trusts.

Why does inventory accuracy matter so much?

Every planning decision in ERP starts from the inventory figure. Material requirements planning (MRP) uses it to decide what to buy and make. If the starting number is wrong, every recommendation that follows is wrong too.

When planners stop trusting the system, they build workarounds: private spreadsheets, extra buffer stock, and manual checks before every order. That costs time and ties up cash, and it undermines the value of the ERP investment. For a wider look at where stock visibility breaks down, see inventory blind spots and how ERP closes the gaps.

What causes inventory errors in manufacturing?

Most errors come from a handful of predictable causes:

1. Late or batched transactions: materials move on the floor, but the system is updated at the end of the shift or the end of the week.
2. Inaccurate BOMs: backflushing deducts components based on the BOM, so if the BOM is out of date, the deduction is wrong every time.
3. Unreported scrap: parts damaged or rejected during production disappear physically but stay in the system.
4. Untracked work-in-progress: materials issued to the floor sit in a gray zone between store and finished goods.
5. Unit-of-measure mix-ups: buying in boxes, storing in packs, and issuing in pieces creates conversion errors.
6. Weak location control: stock is put away in the wrong place or moved without a transfer, so it exists but can’t be found.

Notice that most of these are process problems, not counting problems. A full stock take corrects the numbers once, but the same errors creep back if the causes stay.

How do you measure inventory accuracy?

Measure inventory record accuracy: the share of counted items where the system quantity matches the physical count within an agreed tolerance.

Set tighter tolerances for high-value or critical items and looser ones for low-cost consumables. Track the measure monthly, by item class and location, so you can see where accuracy is improving and where problems cluster.

How do you improve inventory accuracy?

Combine better transactions, smarter counting, and clear ownership:

• Record at the point of activity. Use barcode or mobile scanning when goods are received, moved, issued, and completed, so the system updates in real time.
• Switch to cycle counting. Count a small number of items every day, prioritizing high-value, fast-moving items (often called A items) more often than slow movers. This replaces the disruptive annual stock take with continuous checks.
• Fix the root cause of every error. When a count is wrong, find out why, whether it’s a BOM error, a missed scrap entry, or a wrong location, and fix the process.
• Keep BOMs accurate. Review BOMs whenever engineering changes are made, and check backflush results against actual usage.
• Report production in real time. Shop-floor reporting through a manufacturing execution system (MES) records completions and scrap as they happen, keeping work-in-progress accurate.
• Give the store an owner. Restrict access, control locations, and make accuracy a measured responsibility.

Warehouse technology has moved quickly in recent years. Read how the warehouse has evolved for the bigger picture.

Where should you start?

Start small and focused. Pick your top 50 to 100 A items, count them weekly for a month, and log the cause of every variance. The causes will point you to the two or three process fixes that matter most in your factory.

Once those items are reliably accurate, extend cycle counting to B and C items and roll out scanning to more transactions. Accuracy improves in steps, and each step builds trust in the system.

Make the shelf and the system agree

Inventory accuracy is a process result, not a counting result. Record every transaction where it happens, count your most important items often, and treat each variance as a clue to a process fix. When the shelf and the system agree, MRP recommendations become trustworthy again, safety stock can come down, and planners can stop maintaining spreadsheets on the side. Start with your top A items this month and let the variance log show you what to fix first.

Frequently asked questions

What is a good inventory accuracy target?

It depends on your industry and item mix, but leading manufacturers aim for very high accuracy on critical and high-value items, with slightly looser targets for low-cost consumables. More important than the exact figure is a steady upward trend and tight control of the items that can stop production.

Is cycle counting better than an annual stock take?

For most manufacturers, yes. An annual stock take shuts down operations and fixes numbers once a year. Cycle counting runs continuously without stopping production, catches errors sooner, and reveals their causes. Some companies still need a year-end count for auditors, but cycle counting can reduce its scope.

Does barcode scanning really make a difference?

Yes, because it removes manual typing and records transactions at the moment they happen. Scanning cuts errors in item codes and quantities and closes the time gap between physical movement and system updates, which is one of the most common causes of inaccuracy.

Can inventory accuracy be fixed without a new ERP system?

Often, much of it can. Process changes such as cycle counting, root-cause analysis, and BOM reviews work in most ERP systems. If your current system can’t support real-time scanning, location control, or shop-floor reporting, that is when an upgrade becomes worth considering.

As an Infor Gold Channel Partner, Phitomas helps manufacturers in Malaysia and Singapore build accurate, real-time inventory in Infor CloudSuite Industrial, with cycle counting, barcode scanning, and shop-floor reporting connected in one system. Talk to our team about improving inventory accuracy →